In a painting process of an automotive industry, yield of paint sprayed to an automobile body is generally from 60 to 80% and 40 to 20% of the sprayed paint constitutes a surplus paint to be removed in a subsequent process. The surplus paint sprayed excessively is usually collected in a wet paint spray booth by water washing and the washing water is circulated for re-use.
In the wet paint spray booth, since the surplus paint collected in the washing water has high tackiness, it adheres to a water-film panel, a piping system and a nozzle, and seriously degrades the efficiency of water washing. Moreover, the greater part of the surplus paint settles to the bottom of the booth pit and the bottom of the circulation pit in the spray booth, and the settled paint hardens into a rubbery state with elapse of time to take much time and labor for removal thereof.
For the solution of problems described above, a paint spray booth treating agent as follows has been be added to the washing water:
1) alkali including NaOH or KOH PA1 2) amphoteric metal salts including Zn salt PA1 3) cationic polymers and metal salts, and PA1 4) bentonite (montmorillonite, hectorite)
It is known that sepiolite is added to waste water including oily matters and then the water is subjected to solid-liquid separation. However it is unknown to add sepiolite to the wet paint spray booth treating agent.
Among the conventional wet paint spray booth treating agents mentioned above, the effect of the alkalis for the reduction in the tackiness is not enough. The amphoteric metal salts and the cationic polymers require to be added in large amounts so that concentration of the salts is increased to cause corrosion of materials, The effect of the bentonite for the reduction in the tackiness is not enough so that a large amount of the cationic polymer is required to be added simultaneously.
Japanese patent publication 10-140045 discloses a paint composition capable of removing a toxic substance from a coated article. The paint composition contains a powdery or finely particular activated carbon and at least one kind of an activated carbon to which a toxic substance remover is stuck such as an amine compound or titanium oxide and a powdery or finely particular porous material such as sepiolite or zeolite. W093/02147 (entered into Japanese phase and published as Toku hyohei 6-509371) discloses an agent for removing tackiness of paint which comprises an inorganic aluminum compound and an organic polymer comprising a quaternary nitrogen atom.